1. Field of the Invention
The present invention relates to a method for manufacturing a piezoelectric device which uses a thin film of a piezoelectric single crystal, and more particularly, to a method for manufacturing a piezoelectric device having a membrane structure.
2. Description of the Related Art
Many piezoelectric devices formed from a thin film of a piezoelectric single crystalline substance have been developed. In a piezoelectric device formed by using a piezoelectric thin film as described above, a support member supporting the piezoelectric thin film is necessary in practical use. In addition, the support member as described above, is arranged on one primary surface of the piezoelectric thin film as disclosed in Japanese Unexamined Patent Application Publication No. 2007-228319 and Japanese Unexamined Patent Application Publication No. 2002-534886. In the configuration described above, a structure in which the support member is arranged on an approximately entire region of one primary surface and a structure in which the support member is not arranged only in a region functioning as the piezoelectric device but is arranged only in a region not functioning as the piezoelectric device have been provided. The structure in which the support member is arranged only in a region not functioning as this piezoelectric device is a membrane structure.
As a method for forming this membrane structure, in the past, there has been a method in which after being bonded to the entire primary surface of a piezoelectric substance, a support member arranged in a region functioning as a piezoelectric device is removed by etching or the like.
However, in the method performed by the removal as described above, it is not easy to completely remove the support member only in a necessary region without imparting an adverse influence on the piezoelectric substance. For this reason, as disclosed in Japanese Patent Application No. 2008-282567, a method is disclosed in which, after a recess portion is provided in a support member, and a sacrificial layer material, which can be easily removed, is filled in the recess portion, the supporting member is bonded to a piezoelectric substance so that the sacrificial layer material faces a functional portion of the piezoelectric substance, and after the bonding, the sacrificial layer material is removed. With the method described above, a hollow membrane structure can be more easily achieved as compared to that in the past.
However, since the support member and the piezoelectric substance are pressed together with a high pressure in order to obtain a sufficient bonding force, in the method described above, if a bonding treatment is not performed after the flatness of a bonding plane of the support member in which the sacrificial layer material is filled is sufficiently ensured, the surface of the piezoelectric substance receives a large stress directly from a projection portion of the support member during the bonding, and crystalline destruction of the piezoelectric substance occurs. Thus, the possibility of degradation in the operation of the piezoelectric device cannot be completely eliminated.